Math.random() is not really random on Android

pozirk · January 19, 2017, 1:19am

I have card game where I shuffle cards randomly using Math.random().
It works fine for Flash and Windows target, but on Android target from time to time it returns the same not random results.
Any help with that?
Thank you!

player_03 · January 19, 2017, 1:44am

gist.github.com

https://gist.github.com/player-03/929b900bd78d3ff641578b6e0c670c46

CPPRandomSeed.hx

@:cppInclude('time.h')
class CPPRandomSeed {
	public static function seed() {
		#if cpp
			untyped __cpp__('srand(time(NULL))');
		#end
	}
}

Thomas_Bernard · January 19, 2017, 1:53am

At the beggining of your shuffle function just add:

#if cpp
untyped __cpp__('srand(time(NULL))');
#end

and add

@:cppInclude('time.h')

in the header of your class containing that function

pozirk · January 19, 2017, 8:35am

Wow! Thanks guys for quick help!

singmajesty · January 19, 2017, 5:05pm

Perhaps there’s a way to improve this?

github.com

HaxeFoundation/hxcpp/blob/7bd5ff32b19834ada12d06f1f8bb5ee57b802aa4/src/hx/libs/std/Random.cpp#L78-L112


Dynamic _hx_std_random_new()

{

 rnd *r = new rnd();



#if defined(NEKO_WINDOWS)

#if defined(HX_WINRT) && defined(__cplusplus_winrt)

 int pid = Windows::Security::Cryptography::CryptographicBuffer::GenerateRandomNumber();

#else

 int pid = GetCurrentProcessId();

#endif

#elif defined(EPPC)

 int pid = 1;

#else

 int pid = getpid();

#endif



 unsigned int t;

#ifdef HX_WINRT

 t = (unsigned int)GetTickCount64();

#elif defined(NEKO_WINDOWS)

This file has been truncated. show original

andrew911 · January 22, 2021, 9:47am

Probably need to be fixed somehow, it’s not good that standard library version of random works incorrectly

VishwasGagrani · January 25, 2021, 7:36pm

I use Random library.

haxelib install Random

It’s a small class but solves the problem of output repeating random numbers especially inside a loop.

andrew911 · January 26, 2021, 2:11pm

Yes, I know that alternatives exists, but it’s incorrect behavior in standart library, that will be used by many developers and it’s bad

joshtynjala · January 26, 2021, 5:01pm

Has anyone filed a bug report for hxcpp? Since it’s not a bug in OpenFL, but in a lower level dependency, this thread probably isn’t going to be seen by whoever can fix the issue.

andrew911 · January 26, 2021, 5:47pm

Yes, already there https://github.com/HaxeFoundation/hxcpp/issues/784
Using srand48 instead of srand helps for me